The permanent alteration of the colour of keratinous fibres, in particular human hair, by the application of hair dyes is well known. In order to provide the consumer with the hair colour and the intensity of colour desired, a very complex chemical process is utilized. Permanent hair dyeing formulations typically comprise oxidative hair dye precursors, which can diffuse into the hair through the cuticle and into the cortex where they can then react with each other and suitable oxidising agents to form the end dye molecules. Due to the larger size of these resultant molecules they are unable to readily diffuse out of the hair during subsequent washing with water and/or detergents; hence delivering a consumer-desired permanency of colour. This reaction typically takes place in an aggressive environment at approximately pH 10 in the presence of an alkalizing agent and in the presence of an oxidizing agent. Moreover, the consumer repeats this process regularly in order to maintain the desired hair colour and shade and the intensity of colour and to ensure continual, even coverage of the hair including coverage of new hair growth.
The manufacturer of such products is also required to work within a large number of constraints. Since these products are being placed in direct contact with the consumers' skin, the potential exists for accidental contact with the eye or for ingestion (for example), which can occur during the dyeing process. Therefore, the formulation must meet rigorous safety requirements and not induce any allergic reactions. In addition to meeting these requirements, the products must also be optically and olfactory pleasing to the consumer. In particular, the products also need to meet certain physical parameters in order to ensure that the product can be easily applied to the hair by the consumer to provide the desired effect, without unintentional staining of the consumers' clothes, skin particularly along the hair line or other objects.
The manufacturer is also required to provide the hair colouring consumer a large range of different resulting colours. Some consumers may just wish to enhance the natural colour of the hair, whilst others may wish to cover grey or completely alter the hair colour to a different natural appearing hair colour or a ‘synthetic’ appearing hair colour. Consequently, the manufacturer may provide over twenty different formulations, of varying colours and shades, to address the range of consumer specific needs. These formulations have to be individually formulated and are typically complex formulae containing a mixture of different dye compounds. As a result the manufacture of such product ranges can be costly and complex.
However, despite the fact that commercial hair dyeing products have been available for many years, the products still exhibit a number of consumer-related deficiencies. Typically permanent hair dye products will contain an alkali, typically a source of ammonia. This serves the purpose of swelling the hair allowing the entry of the dye precursor molecules into the hair and also improves the lightening effect of the oxidising agent, which is typically hydrogen peroxide. However, ammonia is also volatile and its associated odour is extremely unpleasant and often irritating to the consumers' of such products, particularly as these hair dye products are used in close proximity to the nasal region. Hence, it would be highly desirable to provide an oxidative hair colouring and/or bleaching composition, which delivers the consumer required lightening level and colour, but which has reduced or eliminated the detectable ammonia odour.
In fact another deficiency area in current hair colouring products is the provision of hair colouring products which deliver the required hair lightening effect. Delivering the required level of lightening is particularly important in order to provide the full range of colour shades demanded by the consumer, especially for blonde shades and grey coverage. Such products pose particular difficulties to the manufacturer, as they usually require the use of high levels of oxidising agent typically hydrogen peroxide and ammonia in order to deliver the required lightening effect. However, the presence of oxidizing agent and/or ammonia may in some cases induce mild sensory skin irritation on the scalp that can be described as stinging, tingling, itching, or burning or descriptors there like. Hence, it would also be highly desirable to provide an oxidative hair colouring and/or bleaching composition which delivers the required lightening and/or colour without the aforementioned sensory scalp irritation.
Moreover, in order to provide a product which the consumer can easily apply to the hair without dripping onto the skin, clothes or bathroom surfaces, hair colourant products are designed such that the composition has a certain required viscosity. This is either achieved by providing the dye composition and the oxidizing composition as so called thin-thin type liquid formulations which are thickened upon mixing or where at least one of the components, either the dye composition or the oxidizing composition, is provided as a thickened formulation which thickens the total composition upon mixing. The said thickened formulation can be achieved by the use of a gel network system which provides the desired thickness to either the dye composition or the oxidizing composition or, preferably, both compositions, while often giving additional benefits of cream-like texture, smooth rinse and improved hair feel. Numerous surfactants can be used to formulate gel network thickened composition. However, these surfactants can also further contribute to sensory scalp irritation described above. Hence, it would be further desirable to provide the consumer with a cream hair colourant, providing improved lift and lightening and improved colour delivery, uptake and durability and which is easy to manufacture, delivering the required viscosity and which is shelf life stable, with a minimal amount of associated sensory scalp irritation.
The use of carbonate has been described in the art to reduce the amount of irritating ammonia odour. For example EP 435 012 describes hair-dyeing compositions, which require a short dyeing time, create little damage to hair, and no irritating odour after dyeing comprising a carbonate source, a non odour generating alkali hydrogen peroxide and a buffer solution. Similarly EP 1 106 166 describes hair dye compositions comprising ammonia, carbonate (other than ammonia salt), transition metal salt and chelating agent which do not give off an irritating odour, have low skin irritation and can change the hair colour into a lighter tone in a short time. WO01/28508 describes hair colouring formulations comprising oxidising agents and ammonia carbonate or carbamate which deliver improved bleaching and colouring with reduced odour and hair damage without the need for buffering agents, pH modifiers or hair swelling agents. JP01206825 describes a low pungent hair colouring composition comprising ammonia, ammonium salt and carbonate. US2004/0083557 describes hair colouring compositions comprising an oxidative hair dye precursor, a metal cyanate, an alkalizing agent and an oxidizing agent and preferably a metal bicarbonate salt in order to provide good colour lift and low odour. DE19721797 describes a process to simultaneously dye and lighten hair comprising the steps of applying a composition comprising hydrogen peroxide, water soluble direct dye or oxidative dye, and at least one substance selected from ammonium carbonate, ammonium hydrogen carbonate, sodium carbonate and or sodium hydrogencarbonate.
WO04/014328 describes one step hair colouring compositions comprising peroxide oxidizing agents, specific oxidizing agents and at least one water soluble carbonate releasing salts which more effectively deliver colour wherein the composition is applied for a period of from 2 to 60 minutes. US2004/0098814 describes a method of permanently colouring hair whereby the hair is subjected to a number of consecutive short treatments whereby the treatment comprises a dye intermediate in a shampoo or conditioner base, a water soluble carbonate releasing salt and a water soluble ammonium salt. US2004/0098816 also describes a method for the gradual permanent colouring of hair which includes subjecting the hair to a number of treatments having a set time interval between them, wherein the treatment compositions comprise ammonium carbonate in combination with a chelant.
However it has now been found that the use of hydrogen peroxide and carbonate hair colourant systems, results in additional difficulties in manufacturing. Hence it would be desirable to provide a hair colorant composition which incorporates high levels of carbonate without compromising the product stability or ease of manufacture, with a minimal amount of sensory scalp irritation.
It has now been surprisingly found that oxidative hair colouring compositions comprising an oxidizing agent, an alkaliser and a specific gel network thickening system as defined herein below, preferably utilised with carbonate at pH 9.5 and below, can be formulated as stable thickened cream systems with minimum sensory scalp irritation on application.
Moreover, the compositions exhibit low odour and deliver a high level of lift and lightening equal to the currently utilised ammonia/peroxide systems, whilst reducing the concentration of peroxide and reducing the hair fibre damage. Furthermore, the compositions of the present invention are compatible with current dyes and dye precursor systems and result in improved lift and lightening for blonde shades, excellent dye deposition and colour and improved grey coverage, whilst also being mild to the skin.